1. Field of the Invention
The present invention relates to the modelling of activity in a computer-modelled environment.
2. Description of the Related Art
Computer games can be played on a number of different types of computer terminal such as a personal computer, specialized games console or even a mobile phone. A typical game involves interaction between an end user and a game world, which is a computer modelled environment comprising a computer-modelled space and computer-modelled objects within that space. The computer-modelled space is effectively a coordinate system within which the computer-modelled objects may extend, move, and be related to one another. In typical modern games, the coordinate system and objects are usually three-dimensional.
In creating a computer game world or other computer-modelled environment, it is desirable that the graphics should be as realistic as possible so that the end-user will feel immersed in that environment. This involves ensuring the realism of not only the immediate, static appearance of objects in that environment, but also the behaviour of activity occurring in relation to those objects, i.e. how things move or change. In the case of a game, the activity could occur either in response to stimulus from the end-user or autonomously.
One such type of activity is the emission of particles from a surface of a computer-modelled object. This may be used for example to model explosions or smoke.
The current technique for emitting particles from a surface is to place a plurality of discrete “emitters” over that surface. An emitter is a dedicated point element within the model, from which one or more particles are emitted.
For instance, in the example shown in FIG. 1a, an explosion is to be modelled to occur from within a building 2. The modelled building 2 comprises a plurality of windows 4 which are defined by portions of the surface of the building 2. To simulate the explosion, a plurality of smoke or dust particles is to be emitted from the windows 4. Therefore, a plurality of emitters 6 is laid down on the portions of the building's surface defining the windows 4. Each emitter 6 emits one or more particles, which represent the dust or smoke particles or such like.
However, in order to achieve a realistic effect, the emitters 6 must each be placed individually in a realistic pattern by the designer who is creating the model (no particular pattern is shown explicitly in FIG. 1a, but it will be understood that this figure is just schematic). This technique is highly time consuming for the designer.
The emitters 6 could instead be placed at random over each window, but that would not create a very realistic effect.
An alternative technique is to place a single emitter 6′ inside the modelled building 2, then emit many particles from that emitter 6′ and calculate for each one where the particle would strike the interior of the building 2 and where it would pass through a window 4. This is shown schematically in the side-on view of FIG. 1b. However, this technique incurs a high processing cost, i.e. requires many processing cycles.
Similar difficulties may be encountered when modelling other kinetic properties of a surface. For example, a surface may be modelled to have a material property defining how that surface deforms in response to impacts, but manually specifying the variations in that material property over the surface may be time consuming for the designer.
It is desirable to find an improved technique for modelling kinetic activity such as particle emission or the like occurring in relation to surfaces of computer-modelled objects.